The present invention relates to a method for detecting failure of a pump assembly, such as a fuel pump assembly in a fuel pump module, which includes a plurality of fuel pump assemblies.
In fuel pump modules, as a rule a fuel pump assembly, for instance an electric fuel pump, is used, which supplies the internal combustion engine with fuel. In modern applications, the supply quantity of a single fuel pump assembly can be sufficient to meet the fuel demand of an engine with normal engine consumption. In vehicles with very high-powered engines and very high engine consumption, two or more fuel pump assemblies, such as electric fuel pumps, can be provided in the fuel pump module in order to meet the greater engine consumption quantity in the full-load situation, for instance.
In fuel pump modules equipped in this way, the failure of one fuel pump assembly can mean that because of inadequate fuel supply in the full-load situation, the impermissibly leaned-down engine will overheat and can lead to a catalytic converter fire, since unconsumed fuel passes through the outlet valves directly into the catalytic converter, which is very hot. This occurs especially at lambda values of 1.2 to 1.5, and in the worst case it can lead to the complete destruction of the engine.
The method according to the invention makes it possible to utilize the continuously detected lambda signal in the exhaust system to ascertain the failure of one of a plurality of fuel pump assemblies, and it protects the engine to be supplied with fuel against overheating and more extensive damage, as well as protecting the catalytic converter, included in the exhaust system, against catalytic converter fire from ignition of uncombusted fuel. Since the requisite sensors for ascertaining the lambda signal, the load state, the rpm, and other engine-specific parameters, such as engine temperature, tendency to knocking, and air temperature, are already present, implementing the invention in an engine requires merely modifying the control program for the control unit.
Along with the selection detection, which in this way is simple to implementxe2x80x94while dispensing with additional structural componentsxe2x80x94for a fuel pump assembly, the safety shutoff of engine-specific different types and model series of internal combustion engines can be implemented and employed.
In an advantageous feature of the method of the invention, the lambda signal is ascertained continuously upstream of the catalytic converter disposed in the exhaust system and is reported back to the control unit by means of the engine management system. The limitation of both the maximum fuel injection quantity and the associated air quantity can be effected in the full-load situation for instance at maximum rpm, where the engine fuel demand is maximal, and leaning of the fuel-air mixture dictated by the failure of a pump assembly would necessarily cause overheating and more extensive engine damage within the briefest possible time.
The limit values for the lambda signal can be ascertained engine-specifically depending on how the engine management system is used. By means of simple software changes, the lambda limit value can be adapted to various requirements in the most various model series of current engines.
In a preferred variant of the method of the invention, the tripping of the limitation of the maximum fuel injection quantity and of the associated air quantity can already be effected whenever the rpm amounts to 80% of the maximum rpm or the throttle valve is opened at least 80% or more, which is always the case in the full-load situation in an internal combustion engine. A further peripheral condition for tripping the limitation of the maximum fuel injection quantity and the associated air quantity can be specified by providing that the throttle valve remains in a constant throttle valve position for a preselectable period of time xcex94t; the full-load conditions are thus not interrupted by any overrunning shutoff, and thus the full-load conditions prevail for a constant period of time. In that case, failure detection for one of the fuel pump modules is absolutely compulsory, because overheating can occur fastest at full load.
Along with the indicated limitation of the maximum fuel injection quantity and the associated air quantity, morexe2x80x94extensive engine damage under conditions of permissible mixture leaning can also be prevented by providing that via the control unit, all the fuel pumping by the fuel pump module is shut off, so that the engine necessarily comes to a stop.
Within the engine management system of the invention, the throttle valve is controlled by the control unit via the throttle valve transducer, as a function of the lambda signal ascertained by the lambda probes, so that at superstoichiometric lambda values, either a limitation of the maximum fuel injection quantity and associated air quantity, or a shutoff of all the fuel pumping, takes place.